Alzheimer?s disease (AD) is a neurodegenerative disorder characterized by cognitive decline and memory loss. It affects approximately 5.5 million Americans, and is the sixth-leading cause of death in the United States. The amyloid cascade hypothesis, caused by proteolytic processing of the amyloid precursor protein (APP), is one of the leading proposals for the cause of AD; however, drugs that target amyloid beta (A?) plaque formation have failed in clinical trials. The failure to produce a drug that treats the underlying cause of AD rather than its symptoms, suggests a gap in our understanding of the pathogenesis of this disease. While APP is most notable as the precursor of A?, pathogenic processing also produces an intracellular peptide (AICD) implicated in RNA polymerase II transcription with the adaptor protein Amyloid Beta Precursor Protein Binding Family B Member 1 (APBB1; FE65). Here, I present preliminary data that supports a novel role for APBB1 in the regulation of the essential process of making ribosomes. Furthermore, ribosome biogenesis has been associated with neuronal growth and viability, and dysfunction in this process has been observed in post-mortem AD patient brains. These observations have led some to propose a link between ribosome biogenesis and the pathogenesis of AD, and this proposal will explore this link through APBB1. First, I propose to probe the mechanism by which APBB1 regulates ribosome biogenesis in a cell culture system (Specific Aim 1). Second, I propose to test the extent to which APBB1 regulates ribosome biogenesis in primary mouse neurons, and contributes to neuronal plasticity and viability (Specific Aim 2). I hypothesize that APBB1, in an AICD-dependent manner, regulates ribosome biogenesis as a cofactor for the transcription of nucleolar genes that are required for ribosome biogenesis. I also hypothesize that APBB1 is required for normal neuroanatomy including dendrite and dendritic spine density and morphology. Finally, I hypothesize that because of APBB1?s role in ribosome biogenesis, its depletion will trigger the nucleolar stress response leading to p53 stabilization and apoptosis. This proposal will both broaden our understanding of ribosome biogenesis in neurons, and also lend insight into the intersection between ribosome biogenesis and AD, opening new potential avenues for drug discovery.